1. Field of the Invention
The present invention generally relates to an apparatus and method of manufacturing a wellscreen for subterranean use in oil, gas, and water wells.
2. Description of the Related Art
The problem of reliably removing particulates from liquids or gasses (production fluids) exists in many types of wells including oil and gas wells, water wells, geothermal wells, and wells for ground remediation. Typical particulates needing to be filtered out are sand and clay including unconsolidated particulate matter, also known as xe2x80x9cformation sandxe2x80x9d. A major problem in producing hydrocarbon fluids from unconsolidated formations is the intrusion of formation sand, which is typically very fine, into production fluid and equipment. The presence of sand in production fluid often leads to the rapid erosion of expensive well machinery and hardware.
Subterranean filters, also known as xe2x80x9csand screensxe2x80x9d or xe2x80x9cwellscreensxe2x80x9d, have been used in the petroleum industry for years to remove particulates from production fluids. They are generally tubular in shape, comprising a perforated inner member or pipe, at least one porous filter layer wrapped around and secured to the pipe, and an outer cover. The wellscreens are used where fluid enters a production string. For example, a common way to achieve the filtration is to mount a wellscreen in the production string near the area of fluid production such that the produced fluid must pass through the filter layers and into the perforated pipe prior to entering the production string and being pumped to the surface.
A typical method of constructing a wellscreen involves wrapping and seam-welding mesh layers of filtering material around a perforated base pipe. An alternative method involves forming a tube of the mesh material, seam welding it longitudinally and then sliding it over the perforated base pipe. The mesh layers typically consist of sintered mesh filter elements and more coarse wire mesh drainage elements. A protective outer shroud consisting of a perforated tube is then placed over the mesh layers and the perforated base pipe and end rings are then welded in place to seal the ends of the filter elements and protective shroud to the base pipe.
There are problems associated with the forgoing wellscreens and their construction. For example, a conventional vacuum furnace used to manufacture the sintered mesh material needed for the filter elements restricts the maximum size of the mesh material, typically to two feet by four feet. This requires multiple sections of the sintered mesh material be welded together to produce filter elements greater than four feet in length. In a wellbore, wellscreen must typically extend as much as one hundred feet to fully access the surrounding formations. This results in many individual sections of sintered mesh material being welded together to form elements of the required lengths. Each layer of mesh must also be individually cut, wrapped around the base pipe, and then seam-welded. These numerous steps result in a labor-intensive process that is both expensive and requires significant manufacturing time.
In addition, the burst strength, or the ability of the wellscreen to withstand radially applied pressure, is limited to the weakest layer. This is important because hydrocarbons and sand from a surrounding formation may enter the wellbore and hit the wellscreen at high velocity. This problem exists in prior art wellscreens because each layer of mesh is individually assembled and there is a tendency for the layers to be extruded through the holes in the base pipe as radial pressure is applied from the outer diameter of the wellscreen. A similar problem exists with the layers being extruded through holes in the outer shroud as radial pressure is applied from the inner diameter of the wellscreen.
Therefore, a need exists for a wellscreen that is less expensive and requires less time to manufacture than conventional wellscreens.
There is a further need for a wellscreen that is more robust and exhibits higher burst pressure than conventional wellscreens.
There is yet a further need for a wellscreen that can be manufactured in a variety of lengths.
The present invention generally relates to an apparatus and method of manufacturing a wellscreen for subterranean use in oil, gas, and water wells. The present invention provides a method of manufacturing a wellscreen whereby layers of porous material are continuously sintered to a perforated metal strip to form a laminate, and the laminate is shaped to form a tube. The tube is then disposed over a base pipe and the ends of the tube are sealed to the base pipe.
In addition, the invention relates to a wellscreen comprised of a laminate shaped to form a tube, whereby the laminate includes a plurality of layers of continuously sintered porous material.
In one aspect of the invention, the laminate is either spiral welded or longitudinally welded into a straight tube.
In another aspect of the invention, the laminate is either spiral welded or longitudinally welded into coiled tubing.